4.4BSD/usr/share/man/cat2/accept.0

ACCEPT(2)                   BSD Programmer's Manual                  ACCEPT(2)

NNAAMMEE
     aacccceepptt - accept a connection on a socket

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<ssyyss//ttyyppeess..hh>>
     ##iinncclluuddee <<ssyyss//ssoocckkeett..hh>>

     _i_n_t
     aacccceepptt(_i_n_t _s, _s_t_r_u_c_t _s_o_c_k_a_d_d_r _*_a_d_d_r, _i_n_t _*_a_d_d_r_l_e_n);

DDEESSCCRRIIPPTTIIOONN
     The argument _s is a socket that has been created with socket(2),  bound
     to an address with bind(2),  and is listening for connections after a
     listen(2).  The aacccceepptt() argument extracts the first connection request
     on the queue of pending connections, creates a new socket with the same
     properties of _s and allocates a new file descriptor for the socket.  If
     no pending connections are present on the queue, and the socket is not
     marked as non-blocking, aacccceepptt() blocks the caller until a connection is
     present.  If the socket is marked non-blocking and no pending connections
     are present on the queue, aacccceepptt() returns an error as described below.
     The accepted socket may not be used to accept more connections.  The
     original socket _s remains open.

     The argument _a_d_d_r is a result parameter that is filled in with the ad-
     dress of the connecting entity, as known to the communications layer.
     The exact format of the _a_d_d_r parameter is determined by the domain in
     which the communication is occurring.  The _a_d_d_r_l_e_n is a value-result pa-
     rameter; it should initially contain the amount of space pointed to by
     _a_d_d_r; on return it will contain the actual length (in bytes) of the ad-
     dress returned.  This call is used with connection-based socket types,
     currently with SOCK_STREAM.

     It is possible to select(2) a socket for the purposes of doing an
     aacccceepptt() by selecting it for read.

     For certain protocols which require an explicit confirmation, such as ISO
     or DATAKIT, aacccceepptt() can be thought of as merely dequeueing the next con-
     nection request and not implying confirmation.  Confirmation can be im-
     plied by a normal read or write on the new file desciptor, and rejection
     can be implied by closing the new socket.

     One can obtain user connection request data without confirming the con-
     nection by issuing a recvmsg(2) call with an _m_s_g___i_o_v_l_e_n of 0 and a non-
     zero _m_s_g___c_o_n_t_r_o_l_l_e_n, or by issuing a getsockopt(2) request.  Similarly,
     one can provide user connection rejection information by issuing a
     sendmsg(2) call with providing only the control information, or by call-
     ing setsockopt(2).

RREETTUURRNN VVAALLUUEESS
     The call returns -1 on error.  If it succeeds, it returns a non-negative
     integer that is a descriptor for the accepted socket.

EERRRROORRSS
     The aacccceepptt() will fail if:

     [EBADF]      The descriptor is invalid.

     [ENOTSOCK]   The descriptor references a file, not a socket.

     [EOPNOTSUPP]
                  The referenced socket is not of type SOCK_STREAM.

     [EFAULT]     The _a_d_d_r parameter is not in a writable part of the user ad-

                  dress space.

     [EWOULDBLOCK]
                  The socket is marked non-blocking and no connections are
                  present to be accepted.

SSEEEE AALLSSOO
     bind(2),  connect(2),  listen(2),  select(2),  socket(2)

HHIISSTTOORRYY
     The aacccceepptt function appeared in 4.2BSD.

4.2 Berkeley Distribution        June 4, 1993                                2